Known methods for detecting the presence of analytes in sample fluids include marking analytes with a label, such as a fluorescence dye, for optical detection of emitted light from the dyes (which may indicate the presence, amount or concentration of the analyte). Emission of light may occur, for example, in response to exposure to an excitation light or when a label is freed from a molecule.
In polymerase chain reaction (PCR), for example, in which target nucleic acids are replicated through a sequence of amplification steps (e.g., melting, annealing, and extension), nucleic acids may be combined with reagents containing fluorescence dyes which can react with the nucleic acids so as to mark the replicated nucleic acids with a dye. In real-time PCR, during each cycle of amplification, dye-marked replicated nucleic acids may be optically detected, for example, by exciting the dyes and measuring the fluorescence signal emitted in response to the excitation light. In some instances, the fluorescence signal obtained may be correlated to the amount of nucleic acid. Commercially available instruments may be used for performing real-time PCR and optical detection of the reaction products.